Metallurgical process



1,633,091 June 21 1927' w. E. GREENAWALT METALLURGICAL PROCESS Filed sept'. v, 1926 OT@ OI Concentrate A 5*@ Ronsmg l u'mace Raw Ftcr Pyrdne Smlnermg Sme H:m g

Furnace Furnace.

Slag 'i Co r M SulphurVapor Sattler No 2 Regeneraccd.

' Acid Soluhon Co per T 11H5 Waace Souhon INVENT Patented` June 21, 1927.

' UNITED STATES PATENT oFFIcE.

WILLIAM E. GREENAWALT, OF DENVER, COLORADO.

METALLURGICAL PROCESS.

Application filed September 7, 1926. Serial No. 134,099.

i The invention is more specifically directed to the treatment of copper ores containingl which are more valuable than the copper or l precious metals. The economical treatment .of such ores in the vicinity of the mines has presented a difficult problem, and if the ores Iare shipped tothe large industrial centers for treatment, the margin of profit to the miner is usually somewhat precarious.

The object of the process is to provide an economical treatment for such ores at the mines, Which is capable of being operated either in very small or in very large umts,

as occasion may require, With the produc` tion of the copper as t-he electrolytic metal and the rare or precious metals in highly concentrated form, or preferably as separate elemental metals, salable direct to the consumer. V

This process may be considered as an improvement or modification of those described.

in my Patents, No. 1,353,995, Sept. 28, 1920,

\ and No. 1,483,056, Feb. 5, 1924, and of my pending application, Ser. No. 6,112, Jan. 31, 1925.

The accompanying flow Sheet, in diagrammatic plan, Will assist in comprehending the process. The processpcan best be described in reference to a hypothetical orewhich. as mined, may be assumed to contain the fol- 1owing metal values: copper 1.5%, gold 0.05

Iz.. palladium 0.10 oz., platinum 0.025 oz., md silver 2.0 oz.

centration or both combined with a highv recovery of the met-als inthe for'm of a sulphide concentrate. Assumlng a preliminar)7 The direct treatment of such an ore for concentration to recover the metal values in the `form of a relatively small amount of high grade concentrate, the concentrate may be assumed, for the purpose of this description, containing 31.25% copper; 1.0 oz. gold; 2.0 oz. palladium; 0.5 oz. platinum; and 40 oz. silver, per ton of concentrate.

Such a concentrate could be shipped land smelted but probably at a prohibitive cost to the miner and he would lose control of the marketing of his product. The concentrate could be smelted direct, but the smelting of a 31.25% copper concentrate to a or mat-te would not be much of an improvement and the expense would be considerable. If the concentrate is roasted and leached, the recovery of the rare or precious metals from the large volume of leached residue by solvent methods alone also presents a difiicult and probably an impractical condition. y

The present method contemplates a departure 'from the ordinary smelting and leaching methods, in which however both methods are employed in such a relation as to conveniently and economically give the copper as the electrolytic metal and the rare or precious metals in a highly concentrated or in elemental form.,

In carrying out the process, the concentrate is carefully roasted so as to make a large portion ofthe copper soluble in Water and a very large portion soluble in a dilute acid solution. It is diiicult to roastsuch a high grade concentrate to get over 95% to 98% extraction of the copper by ordina leaching methods. For the purpose of this process a higher extraction is not necessary, nor. is it desirable.

The roasted concentrate is then leached with Water or a dilute acid solution to eX,- tract the copper. The copper which is soluble in Water or dilute acid is easily and quickly extracted. The rare or precious metals remain in the residue.

, The copper solution from the leaching tank, containing salts of iron, flows into the SO2 reducer, where ferrie iron is reduced to the ferrous condition by the SO2 obtained froml roasting the sulphide concentrate. The reduced solution' then flows into the storage or settling tank No. 1, where the ferrie iron is still further reduced by the small excess of SO2 dissolved in the solution, and the solution isclarified. The solution then flows into the copper tanks No. 1, Where the copper is deposited as the electrolytic metal 'with the simultaneous regeneration of acid regenerated. A portion .of the solution from Y the copper tanks No. 2 is returned to the `SOzreducer. No. 2, While another portionthe advance ioW-is returned to the roasted concentrate to pass throu h another complete cycle. In this Way t e copper is extracted from the roasted concentrate and is lconverted into the electrolytic metal. When the vcopper in the concentrate has been suiiiciently extracted, the concentrate residue is ready for the next step in the treatment. The amount of copper it is desirable to keep in the residue Will be determined by the operator and will have to-be determined by experience. Usually it will be the copper Which is not readily soluble in an acid solution, and this Will usually be the desired amount for the succeeding step in the process, altho the residual copper `in the leached concentrate residue ma vary within wide limits Without interferlng with the successful operation of the process. A fair basis would be an extraction of 30% of the 31.25% ofthe copper in the concentrate, or an extraction of 96%, or 600 pounds of copper per ton of concentrate.

If the capacity of the plant is assumed as ten tons per day, the daily output of electrolytic copper from leaching the roasted concentrate Wouldbe 6000 pounds. Theresidue would still contain 1.25% of the 31.25% copper in the original concentrate and all of the rare or precious metals. But the residue will not Weigh more than half of the original concentrate, since most of the copper has been extracted, the sulphur which Was originally combined with the copper has been eliminated, the sulphur which was combined With the iron has been exchanged for 4 oxygen, and other volatile and soluble constituents of the original concentrate have been removed in the roastingand leaching. The residue may now be assumed to weigh half as much as the original concentrate, but it Will contain all of therare or precious metals and will assay 2.5% copper, Which represents the 1.25% of the 31.25% in the original concentrate. i

In cyclically leaching the roasted copper concentrate with van acid solution and electrolyzing the resulting copper solution containing salts of iron, the solution Will ultimately become foul. A" certain amount of the solution lis therefore diverted from the leaching and electrolytic circuit and the copper precipitated therefrom and the solution Wasted. A certain amount of Washv'vater is added to make up the loss, and this Wash- Water also tends to greatly reduce the soluble copper content of the leached residue,but will not removeall of the soluble. copper.

In order to avoid Waste Washwater complications, the residue after it is leached and partly Washed as described, is treated with lime to neutralize the solution and to precipitate the soluble copper in lthe residue.

The'residue is then filtered or dewatered in containing enough silica to flux off excess iron. SuchY a procedure will give a clean slag and the metal values will be in fairly concentrated form. If one smelting is not suiiicient to give the concentration desired, the first matte may be resmelted, so that the matte will be largely or entirely in the form of CuS or CuZS, containing little or no iron, altho it Will be difficult to eliminate the iron entirely. It is desirable for the best opera-` tion of the process to eliminate it as much as practical. Ifiresmelting of the first matte is necessary, the slag from the second smelting may be added to the first smelting charge of another lot. In this Way a very high recovery of the copper and rare or precious metals maybe made from thejleach residue in the form of a highly concentrated matte and at a relatively small cost for smelting. It should be remembered that the residue `smelted is only half that of the original concentrate. y y

Disregarding the small loss in smelting, the matte Will consist principally of 250 pounds of copper with the combined sulphur of from 150 to 175 pounds, or say 37 5 pounds in all, and this matte or copper sulphide will contain all of the rare or precious metals, or approximately, copper 250 pounds; gold 10.0 oz.; palladium 20.0 oz.;

platinum 5.0 oz.; and silver 400 oz. It will have an approximate value of $2,600.00, and Will permit of careful and economical treatment to recover the various metals in mar ketable form. f

The small portion of high grade matte. Weighing about 375 pounds, is introduced into an electric furnace, preferably in hot fluid form as it comes from the smelting furnace. The temperaturev is raised in the electric furnace -to dissociate the copper and sulphur. The sulphur of the CuS is volatilized at a comparatively low temperature, but it requires a high temperature-practically a White heatto volatilize the sulphur ofthe CuzS. The volatilized sulphur, as

sulphideris governed by the temperature, and y -sulphur vapor, maybe combined ywith hydrogen toform hydrogen sulphide, and the hydrogen sulphide so produced may be used to precipitate copper. from lean and foul .Y

solutions.

vBy properly' adjusting the temperature in the electr-1c furnace and the time of treatment the copper matte or copper sulphide can be reduced to the impure metal or as the metal mixed with a relatively small amount of sulphur, or mixed with as much sulphur as practice vvill. show to be the most convenient and the ymost economical. The resulting impure copper is cast into anodes and electrolytically refined, preferably and conveniently by using the rich copper solution from leaching the roasted copper concentrate as the electrolyte. For this purpose the rich copper solution may be taken from -the leaching tank, and iowed through the refining tanks, Aand back to the leaching and electrolytic circuit at a rate determined by practice to be the best. will be deposited as the pure electrolytic 'metal in an electrolyte which can easily be kept at a desired standard of acidity orl of soluble impurities. `The soluble impurities `will not usually be of the harmful kind, such as arsenic, antimony and bismuth. .The rare and precious metals, being insoluble in a sulphate electrolyte, Will accumulate inthel bottom of the copper tanks, and when the accumulation, in the form of anode slimes, is sufficient, the slimes may be removed and refined to separate, orrecover, the rare and precious metals in elemental or marketable form.

.The copper matte,y as derived from the smelting furnace, and consisting largely or entirely of CUS and Cu2S,if introduced intol the electric furnace in a hot fluid condition,

`requires only a relatively7 small amount of heat to elevate and maintain the matte at the dissociation temperature of the copper and ,sulphurl rlhe rapidity of dissociation of the cuprous "the temperature is regulated by the electric current. If steam is' introduced into the electric furnace, a mixture of sulphur and hydrogen sulphide Will issue from the furnace. It is preferred to combine the steam or hydrogen With the v.sulphur outside of the furnace. f p

Hydrogen sulphidebegins to dissociate'at abouttOO deg. C., and increases With the rise in temperature. Carefulh regulation of the combining gases is important, and the temperature of the gases should not greatly exceed 4500 deg. C. to prevent dissociation of hydrogen sulphide. f

While the regulation .of the temperature et the cuprous sulphide in' the electric furnace isfquite easy, the regulation of the temperature of the gases in the furnace is quite sulphur. f

To meet this condition, the gases are The copper of the anodes difficult, if not impractical, to get the maximum amount of hydrogen sulphide with a minimum amount of free hydrogen and free passed through the HZS generator, Where the conditions for the maximum production of hydrogen sulphide canbe controlledand regulated. The temperature may be maintained to get the maximum formation vof hydrogen vsulphide from the uncombined -hydrogen and sulphur vapor, with the minimum amount of disintegration of the hydrogen sulphide. In addition to the close regulation of temperature, the H2S generator may and usually Will contain material which promotes the formation of hydrogen sulphide, such as pumice or glass, either vof Which appears to' act as a catalyst. The generator may consist of a tube orchamber, containing a catalyst, such as pumice, which may be heated indirectly through the Walls of lthe chamber, or directly by an electric current, to the desired temperature, or say, from 400 to 500 deg. C. The mixture of hydrogen sulphide, 'hydrogen or steam, and

sulphur vapor is passed through the H2S 1 generator to combined 'the uncombined hydrogen yor steam With the uncombined lsulphur vapor to` form an equivalent of hydrogen sulphide. The gas is then'y used to precipitate the copper or other metals from solutions, especially from Waste foul copper solutions and lean Wash Waters.

The HZS generator may conveniently consist of a chamber or tube filled with coke, as Well as other material, and heated to the, desired temperature by means of an electric current. 4In this Way the desired reducing 'conditions may be maintained and the temperature may be closely regulated to get a maximum amount of hydrogen 'sulphide from the sulphur vapor from the 'electric furnace.

In the production ofhydrogen sulphide, y

either in the electric furnace or in the HZS ico' generator, a hydrocarbon, preferably in the form of oil, may be' used with or Without steam andy forms a convenient Way of supplying hydrogen ora hydrogen containing fluid and maintaining' the reducingv vatmosphere desired for good operating conditions.

Excellent results can be obtained .by ,introducingvhydrogen or a hydrogen containing uidnto the electric furnace or into the yILS generator. 7 The source of hydrogen which is best available for any particular condition would naturally be used. A

The, hydrogen sulphide is appliedto the copper solutions in vthe H; precipitator,

Whe'rethe cop er land some of the. other met-v als are;precipitatedN from the solutions, with 'the simultaneous regenerationA of acid. The

solution, with the copper sulphide in suspension, flows into the CuS separator, where the CuS is separated from the barren solution. The CuS is preferably applied to the yelectrolyte of the leaching and eleotrolytic circuit, Where it may be used to reduce the ferrie iron produced by the electrolytic deposition of the copper to the ferrous condition, While at the same time the copper of the precipitate is converted into the electrolytic metal, as described more fullyv in my Patents, No. 1,340,826, May 18, 1920, and N0.1,357,495,Nv.2,1920.

It Will be seen, in treating ten tons of concentrate per day, that only about five tons of residue is smelted, including the pyritic addition to the charge; that the five tons of leached residue Will be concentrated and that by treating the matte in the electric furnace to dissociate the copper and sulphur, the resulting impure copper Will Weigh about 250 pounds and contain Yall of the rare or precious metals originally in the ten tons of concentrate. In this form the rare or precious *metals are easily and cheaply separated fromthe copper by electrolysis, with the copper in the' form of the electrol'ytic vrmetal and the rare or precious metals in a highly concentrated condition from vwhich they can easily be separated, or recovered, from one another.

Invsmelting. the five tons of leached residue, the copper necessary for collecting fthe :rare or precious metals may be kept quite low. The copper content of the smelting charge Will'` largely be governed by the amount of copper which is not easily extracted by leaching, and, as all, or'practically all, of the copper remaining inthe leached residue is recovered by smelting, thel roasting and leaching of the concentrate need not be as carefully carried' out as Would be necessary under other conditions, and theoperator can determine the suflic'iency of the extraction of the copper by -leaching'to best carry' out the/process as a Whole.- e

With the small amount of copper in leached residue, the slag from'` the smelting Will be lvery low in copper, especially as con.

trasted with a slag -if the concentrate contain1ng.31.25% copper were smelted,- and the matte, 1n smelting the residue, Willbe adv justed so-as to make a high recovery of the rare or precious metals as Well asfthe copper.

' In re-smelting" the matte, or -its concentration or conversion in the electric furnace,

the slag will contain appreciable valuesl in copper an'd thevrare or vprecious metals, and this slag is returned to the smelting furnace. This procedure makes possible a high recov- -c'ry of the metals, and. gives a. concentrated Qmatte, containingv little or no iron, for4 further treatment. It is preferred t'o run the high grade matte from the smelting furnace in a molten condition into the electric furnace. This insures economy of-fuel and enthe .electrolysis lto deposit the copper as the eleci by smelting into about 375`pounds of matte ;Q trolytic metal, and recoveringth-e rareV or has been sufficiently extracted by leaching smeltingy the residue to concentrate the re-i into an impure copper, casting the resulting ,impure copp-er into anodes, and refining-said anodes in an electrolyte obtained `from leaching the roasted copper concentrate.`

sidual copper and the rare or. precious metalsI 3`;`A process of treating copper concen-l trate containing rare or precious metals'comprising, roasting -the c'oncentratea leachingy the roasted concentrate with an acid solution to extract the copper,'electrolyzing the lresulting copper solution to deposit the copyper and regenerate acid, returning the regeneratedy acid solution to the roasted concentrate and repeating the cycle until the copper has been sufficiently extracted from the roasted concentrate, then smelting the vresidue to v` coppermatte, heating the resulting matte in an electric furnace-to dissociate the copper and sulphur, electrolyzing the resulting impure copper product -to obtain the copper as the electrolytic metal, and itreatingvthe resulting residue to recover the rare or4 precious metals. ,A Y

4. A process of treating copper concentrate containing rare onprecious metals comprising, .ioasting'the concentrate. leaching the roasted concentrate to extract the copper,

sociatethecombined copper and sulphur, ap'-` f plying a'hydrogen containing fluid to the.'

resulting sulphur ivapor to'form hydrogen sulphide, and precipitating copper from the leach copper solution With'said lhydrogen sulphide.

5. A process of treating coppericoncien'-l trate containing rare'or precious metals comprising, roasting the concentrate, leaching the roasted concentrate to extract the copper, then When the copper in the roasted convcopper concentrate as the electrolyte. 6. A process of treating copper concen-v trate containing rare or precious metals com prising, roasting the concentrate, leaching theroasted concentrate with an acidgsolution to extract the copper, vthen whenv the desired portion of the copper has lbeen extracted addinga caustic alkalito theresidue, filtering the residue, smelting the residue to concentrate the residual copper and the rare or precious metals into a matter, dissociating the copper and sulphur of the matte in an electric furnace, and -treating the result-y ing impure copper to obtain the copper as `the electrolytic metal and the .rare or precious metals as the elemental metals.

7. A process of treating copper concen tratel containing rare or precius metals comprising, roasting the concentrate, leaching the roasted concentrate to extract the copper, then when the copper in the vroasted concentrate has been suiiiciently extracted by leaching adding a pyritic material to the:

leached residue, smelting the mixture of residue and pyritic material to concentrate the copper an the rare ripreciousv metals of the mixture into a matte, heating lthe matte to dissociate copper and sulphur, casting the resulting impure copper product into anodes y and electrolytically refining said' anodes to recover thev copper as the electrolyticmetal, and recovering the rare or from the anode residue.

8. A process yof treating -copperconcen'- trate containing rare or precious metals cornprising, roasting the concentrate, leaching the roasted vconcentrate with an aicid solution to extract the copper, electro'lyzing the resulting copper solution to deposit the copper and' regenerate acid, returning the regenerated acid solution to the roasted con-Y centrate and repeating the cycle until the copper has been siliciently extracted, then l-smelting the residue into a concentrated copper product containing'the rare orl precious metals, and electrolytically refining said con'- centrated copper product in an electrolyte obtained' from r,leaching the roasted copper concentrate.

9. A process of treating copper vconcentrate containing'rareor precious metals com-v prising, roastingthe concentrate, leaching precious vmetals the roasted concentrate with an acid solution to extract a portion of the copper, then when the desired portion of the copper has been extracted by 'leaching adding a caustic alkali to the residue, filtering the residue, sintering the residue, smelting the* sintered material to concentrate the .remaining copper in the residue into a matte containing the rare or precious metals, dissociating the coppenand sulphur of the matte in an'electrlc furnace, casting the resulting iinpure copper into anodes, and then electrolytically refining said anodes in the leach copper solution as the electrolyte.

l0. A process of treating copper concentrate containing rare or precious metals comprising, roasting the concentrate, leach'- f ing 'the roasted concentrate to extract the copper, then When the copper in the roasted concentratehas been suliiciently extracted by leaching 'smelting the roasted concentrate f residue -to 'obtain the residual copper `and v,the rare or Iprecious metals in a copper matte, heating the matte in a'reducing ornon-oxidizing 'atmosphere tol dissociate the copper and sulphur, subjecting the/resulting crude copper containing 'the rare or precious metals to electrolysis to deposit the copper -as the electrolytic metal and recovering the rare or precious metals'from the residue,y applying a hydrogen/i containing' Huid to the dissociated su phurnto form hydrogen sulphide, and precipitating copper from the leach solutions with Ysaid hydrogen sulphide.

, trate containing rare or f precious metals comprising, roasting the concentrate, leaching the roasted concentrate With an acid solution to extract` the copper, electrolyzing t theiresulting copper solution` to deposit the copper fand regenerate acid,- returning the'v 11. A process of treating copper concenf regenerated acid solution to the roasted concentrate and repeating the cycle until the copper has been suciently extracted, then ying the copper matte in an electric furnace smelting the residuev to copper. matte, .heatto dissociate the copper and sulphur, casting L the resulting 'impure copper into anodes,

subjecting vthe anodes to electrolysis kto recover thecopper asthe electrolyticmetal, and recovering the rare or precious metals from the residual) anode slimes.

, 12. A process of treating copper concentratecontaining rare or precious 'metals 7- comprising, roastingf the concentrate, leaching the roasted concentrate with an acid solution, separating a portion of the disfsolved copper from the resulting residue and precipitating y the co per therefrom, precipitating another portion vof, the ldissolved lcoppe'r in the leached residue, smelting the residue to 'concentrate' the residual copper into animpure metal containing .the rare or precious metals, and electrolyzing leo iis'

esY

the impure copper to separate theI copper andthe rare or precious metals.

13. A process of treating copper concentrate containing rare or precious metals comprising, roasting the concentrate, leaching the roasted concentrate to extract a portion of the copper, smelting the leached concentrate residue to concentrate the remaining portion of the copper into a matte containj -ing the roasted concentrate to extract a portion of the copper, adding a pyritic material 'f to-the leached concentrate residue, smelting the mixture to concentrate another portion of the copper. into a copper matte containing the, rare or precious metals and Wasting the resulting slag, re-smelting the matte to still further eliminatel impurities and to still further concentrate the copper and the rare or precious metals, adding the `slag from the re-smelting of the matte t-o a new smelting charge, and treating the resulting concentrated copper product from the matte to Aseparate the rare or precious metals from 15: A process of treating lcopper concentrate containing rarey or precious metals comprising, roasting the concentrate, leaching the roasted concentrate 'to extract the` copper, then When the copper in the roasted concentrate has been suiiiciently extracted, adding lime tothe residue, iiltering the residue, adding a pyritic material to the residue, `smeltinguthe mixture, of residue and pyritic' material into a copper matte containing the rare or precious metals, treating the matte to obtain the copperas the impure metal, casting 'the impure copper into .anodes, and reiining said anodes in an elec-" I per concentrate, leaching the roaste trolyte' obtained from leaching the roastedy copper concentrate..

16.- Ay process comprising, roastin `copcentrate with an acid solution to extract the copper, smelting a,copper bearing Inaterial containing rare or vprecious metals to concentrate the rare or precious metals into conan impure copper,'casting the impure copper containing the rare or previous metals into anodes, and relining saidv anodes in an electrolyte obtained from leaching the roasted copper concentrate.

17. A process of Atreating copper concentrate containing rare or precious metals comprising, leaching the concentrate `to extract the copper, smelting the leached concentrate residue to concentrate 'the .residual copper and the rare or precious metals into a matte, electrically heating the matte to dissociate the sulphur of the matte, combining hydrogen l`With the resulting sulphur vapor to form hydrogen sulphide, and precipitating copper from leach solutions with said hydrogen sulphide.

18. A process of treating copper concentrate containing rare or precious metals comprising, roasting 'the concentrate, leaching the roasted concentrate to extract the' copper, adding a pyritic material. to the leached copper concentrate residue, smelting the mixture of leached residue' and pyritic materialv to concentrate the residual cop- `per and the rare or precious metals into a matte, vintroducing thel hot fluid matte into an-electric furnace and heating the matte to dissociate the sulphur of the matte,-and treating the resulting impure copper to separate the copper and the rare or precious metals.

19. A process of treating copper concentrate containing rare vor precious metals comprising, roasting theconcentrate, leaching the roasted concentrate to extract the copper,smelting the leached vroasted concentrate residue to concentrate 'the residual copper andthe rare or precious metals into a copper matte, electrically heating the resulting matte to eliminate lthe sulphur of the matte, and treating the resulting impure copper to separate the copper and the rare or precious metals. A

20. A process of treating copper concentrate' containing rare or precious metals comprising, leaching the concentrate to extract the'copper, smeltingthe leached con` centrate residue to concentrate the residual copper andthe rare or precious metals in'to a matte, treating the matte to eliminate iron and .to further concentrate the matte in copper sulphide, electrically heating the resulting concentratedmatte to eliminate sulphur, and treating the resulting impure copper product to separate the copper and the rare or precious metals.

WILLIAM E; vGerini-iin'iWAL'r. 

